In a conventional retaining wall design, one of the major design considerations is whether the existing terrain will require a cut into the existing ground or fill to create a higher elevation for a new structure such as a road or railway. There are several different retaining wall styles that fall into either deep or shallow foundation walls. In cut situations, typically a deep foundation wall such as a soldier pile retaining wall is preferred since the wall can be constructed with a minimal cut into the existing soil versus a shallow foundation wall such as a mechanically stabilized earth wall which requires a large excavation or cut into the existing ground for straps or ties which will then need to be backfilled with expensive select aggregate. These ties can also be a problem for future maintenance when there is limited space and the straps lie under a future road or railway.
Deep foundation systems generally provide an alternate solution which does not require tieback stabilizing features to oppose the lateral force of the soil. Thus, such systems can be highly advantageous where property lines or site conditions limit the horizontal footprint of the system. Such systems can also be especially useful where adverse soil conditions are near the surface or large loadings on the wall require more stable soil that is typically found at lower depths. Deep foundation systems typically consist of wall panels or laggings that span vertical columns (posts or piles) that can be either driven into the ground or embedded into concrete filled drilled holes. The columns can either cantilever out of the ground or can be anchored back with one or multiple tie rod(s) at various depths of the column. As the earth is filled along the back of the wall, the panels carry the load horizontally to the columns which extend vertically carrying the load deep into the ground and also into the anchors, when utilized.
As walls grow in height upwards of 15 feet, soldier pile walls become expensive due to the exponential nature of soldier pile design which requires huge steel rolled shapes to resist the large overturning moments due to the lateral forces from earth, wind, and/or vehicle surcharge amongst other forces. A composite design which ties the column to the face panel or lagging would reduce this cost. The installation of such known deep foundation post and panel retaining walls, however, is generally a time-consuming process that involves several steps, including for example, selecting a column spacing, determining the optimum length and diameter of the columns, embedding the columns into the holes and then subsequently returning to set the panels between the columns. In addition, the panels of such systems are typically designed as “simple spans” between the columns which must be lifted and moved into position and separately secured to the already installed exposed columns. Altogether, this process can be considerably labor-intensive and can increase the costs and installation time of retaining wall installation projects. Such disadvantages can in turn make deep foundation systems impractical and/or cost prohibitive.
Thus, in view of the foregoing, it would be extremely useful to have a deep foundation precast retaining wall system that can be easily installed and used in connection with a variety of locations and that is sufficiently robust to resist lateral pressures from the retained soil by utilizing multiple spans versus the conventional simple span. It would be further desirable if such structure could be economically fabricated and installed such that labor and material costs that are typically incurred in connection with retaining wall projects can be reduced, while also concealing the support columns for a cleaner aesthetic. From the following description, it will be recognized by persons of ordinary skill in the art that embodiments of the subject invention can provide such benefits as well as other objects, features of advantages.